Underhearth cooling system

ABSTRACT

An underhearth cooling system for a blast furnace has a plurality of cooling tubes passing through the furnace shell and hearth refractories. Water from a shell spray cooling system is collected in a trough. Discharge lines, each with a control valve and an expansion joint connect the trough to each tube which enters the shell through a gas tight stuffing box. A water collection trough at the tube outlet end empties into a discharge tank over an adjustable weir.

United States Patent [191 Jernigan UNDERHEARTH- COOLING SYSTEM [75] Inventor: James A. Jernigan, Upper Saint Clair Township, Allegheny County,

[73] Assignee: United States Steel Corporation, Pittsburgh, Pa.

[22] Filed: Jan. 17, 1974 [21] Appl. No.: 434,159

[52] US. Cl 266/32, llO/l C, 432/238 [51] Int. Cl ..C21b 7/10 [58] Field of Search 266/24, 25, 32, 43;

[56] References Cited UNITED STATES PATENTS 3,386,720 6/1968 Fritz 266/43 X Jan.7, 1975 3,820,770 6/l974 Snow 266/43 Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-Rea C. Helm [57] ABSTRACT An underhearth cooling system for a blast furnace has a plurality of cooling tubes passing through the furnace shell and hearth refractories. Water from a shell spray cooling system is collected in a trough. Discharge lines, each with a control valve and an expansion joint connect the trough to each tube which enters the shell through a gas tight stuffing box. A water collection trough at the tube outlet end empties into a discharge tank over an adjustable weir.

3 Claims, 5 Drawing Figures PATENTEDJAH 71975 SHEET 2 OF 3 PATENTEDJAH 1191s SHEET 3 OF 3 UNDERHEARTI-I COOLING SYSTEM This invention relates to the cooling of shaft furnaces and more particularly to an improved underhearth cooling system for iron-producing blast furnaces.

Large blast furnaces utilizing carbon in place of high duty refractory brick for at least part of the hearth bottom and linings require underhearth cooling because of the size of the hearth and the thermal conductivity of the carbon. Cooling water is sprayed on the furnace shell retaining the hearth and is collected in a trough surrounding the shell. The cooling water in then discharged from the shell cooling trough through discharge pipes to an underhearth cooling inlet trough on one side of the hearth. Some of the discharge pipes are equipped with control valves. The cooling water then flows through a series of tubes passing through the hearth into an outlet trough on the other side of the hearth. Each tube ends in a water box in the outlet trough which provides a dam to create full flow of water in the tube. The outlet trough discharges into a water return tank. The tubes pass through stuffing boxes at the hearth shell on each end of the tube for a gas seal. Both inlet and outlet troughs are rigidly connected to the tubes by welding.

This system does not provide for differential thermal expansion of the tubes. The tubes remain full even when there is no water flow which continues to remove heat from the bottom. The arrangement has no provision for balancing the flow of water through the system.

It is therefore an object of my invention to provide an underhearth cooling system in which the water flow may be balanced.

Another object is to provide such a cooling system in which the water level in the tubes may be changed.

A further object is to provide such a cooling system that allows for differential expansion of the underhearth cooling tubes.

These and other objects will become more apparent after referring to the following drawing and specification in which FIG. 1 is a sectional plan view of a blast furnace hearth with the cooling system of my invention,

FIG. 2 is a partial sectional view along line [1-1] of FIG. 1,

FIG. 3 is a partial sectional view along line III-III of FIG. 1,

FIG. 4 is a partial sectional view along line IV-IV of FIG. 1, and

FIG. 5 is a sectional view showing a stuffing box for a cooling tube. 8

Referring now to the drawings, reference numeral 2 is a foundation upon which the hearth is built. A plate 4 covers foundation 2. A shell 6 projects upwardly from plate 4 and surrounds the hearth bottom blocks and wall linings 8 which may be carbon brick or carbon block and in combination with high duty refractory brick. Surrounding shell 6 are one or more spray cooling headers 10 which provide a water cooling spray 12 on the side of shell 6. Water from spray 12 is collected in a shell cooling trough 14 which surrounds shell 6.

A plurality of parallel stainless steel cooling tubes 16 pass through the hearth and shell. Each tube 16 is connected to cooling trough 14 by a discharge line 18. Each discharge line 18 includes a control valve 20 and an expansion joint 22 which may be a conventional expansion joint using high temperature flexible fluorocarbon materials. Pipe 16 enters the hearth and shell through a stuffing box 24 welded to shell 6. Conventional asbestos lattice braid packing material 26 is used for packing in stuffing box 24. Tube 16 leaves the hearth with a gas tight welded connection 28 to shell 6 and is connected to a water collection trough 30 extending partially around the shell.

Cooling water flows from trough 30 over an adjustable weir 32 into a discharge tank 34. Cleanouts 36, located in the wall of trough 30, are provided for tubes 16 except at the location of weir 32. A drain 38 con nects trough 30 to discharge tank 34. An overflow drain line 40 connnects trough 14 to discharge tank 34. Discharge tank 34 has a drain line 42 connected to other parts of the cooling system, not shown. A tube 44 runs through the hearth and contains thermocouples 46 connected to a temperature indicator, not shown.

Cooling water from sprays l2 flows down the outer face of shell 6 and collects in shell cooling trough 14. Each valve 20 is adjusted to supply the desired flow rate of water in the particular tube 16 to which it is connected. By adjusting valves, the cooling effect can be balanced throughout the hearth area. The hearth thermocouples 46 indicate when valve positions should be changed. For example, when refractories need to be cooled to prolong their life, more cooling water is put through the tubes. Conversely, when the furnace is not in production, less water is put through the tubes to avoid solidifying the salamander above the iron notch.

The height of weir 32 is set so that the tubes are full of water at normal flow and less than half full with no flow. This adjustment minimizes unnecessary heat losses through the furnace bottom at times when the furnace is not in production and valves 20 are turned off. The height of overflow drain 40 along the wall of trough 14 is selected so that there is normally sufficient water in trough 14 available for the tubes 16, and drain 40 will handle the shell cooling water when valves 20 are either off or set for low flow rates.

A single stuffing box 24 is used for each tube l6 which reduces considerably the potential for gas leaks. Stuffing box 24 and expansion joint 22 allow for differential thermal expansion of tubes 16.

While one embodiment of my invention has been shown and described, it will be understood that modifications may be made within the scope of the invention.

1 claim:

1. An underhearth cooling system for a blast furnace having a shell surrounding the hearth refractories comprising a plurality of cooling tubes passing through the shell and the lower hearth refractories,

a cooling water inlet trough located above the cooling tube inlet ends,

a discharge line for each cooling tube connecting the bottom of the cooling water inlet trough to the cooling tube inlet end,

an expansion joint in each discharge line,

a control valve in each discharge line,

a stuffing box surrounding each, cooling tube at one location where the cooling tube passes through the shell, and

a water collection trough connected to the cooling tube outlet ends.

2. A cooling system according to claim 1 which includes a spray cooling system for the furnace shell in the hearth area with said cooling water inlet trough mounted on said shell to collect cooling water from the spray cooling system flowing down the sides of the shell and an overflow drain connecting the cooling water inlet trough to the discharge tank. 

1. An underhearth cooling system for a blast furnace having a shell surrounding the hearth refractories comprising a plurality of cooling tubes passing through the shell and the lower hearth refractories, a cooling water inlet trough located above the cooling tube inlet ends, a discharge line for each cooling tube connecting the bottom of the cooling water inlet trough to the cooling tube inlet end, an expansion joint in each discharge line, a control valve in each discharge line, a stuffing box surrounding each cooling tube at one location where the cooling tube passes through the shell, and a water collection trough connected to the cooling tube outlet ends.
 2. A cooling system according to claim 1 which includes a discharge tank connected to the water collection trough for receiving water from the water collection trough and an adjustable height weir over which cooling water flows from the water collection trough into the discharge tank.
 3. A cooling system according to claim 2 which includes a spray cooling system for the furnace shell in the hearth area with said cooling water inlet trough mounted on said shell to collect cooling water from the spray cooling system flowing down the sides of the shell and an overflow drain connecting the cooling water inlet trOugh to the discharge tank. 